1. Field of the Invention
The present invention relates to an underwater housing for a camera in which photographic film is wound up manually, and to the combination of such a housing with such a camera.
2. The Known Prior Art
A lens-fitted film unit or single-use camera is preloaded with photographic film before a user purchases it. After he takes photographs by use of the film unit, he does not need to unload the photographic film from the film unit. He can forward the film unit containing the exposed film to a photo laboratory where a photofinisher unloads the photographic film and performs photofinishing. Such convenience and simplicity in use is a characteristic feature of the film unit, which is sold commercially in a large scale.
For the purpose of using the film unit even underwater, there has been proposed an underwater housing for containing the film unit, as disclosed in Japanese Patent Laid-Open Publn. No. 2-203329. In such an underwater housing, there is mounted a manually operable dial on an upper side of a housing body for winding up the photographic film. The dial is provided with a coaxial gear, which is coupled directly with a film wind-up dial of the film unit. When the film unit is used without an underwater housing, the wind-up dial is rotated directly with the user's finger.
To wind up the photographic film while the film unit is contained in the above-described underwater housing, the dial on the housing needs to be manually rotated in the direction opposite to the direction of rotating the wind-up dial on the film unit. If the user is accustomed to using the film unit without the underwater housing, he might rotate the dial of the underwater housing in the wrong direction inadvertently. There is also a problem in that the dial on the housing projects largely rearwardly from the housing body, because the housing dial is coaxial with the coupling gear in mesh with the wind-up dial on the film unit. To reduce such rearward projection of the housing dial, it needs to have a small diameter. Such a small housing dial is, however, pinched between the user's fingers when it is rotated. This construction increases the force that must be applied by the user, so that the user cannot wind up the photographic film rapidly. Because such a small dial is awkward for the fingers to manipulate, there is the danger of applying excessive force to the housing dial and in turn to the film-advancing mechanism, so that this mechanism might be damaged.
Referring to FIG. 10 illustrating a lens-fitted film unit 2 and a manually operable dial 53 of the conventional underwater housing, a wind-up dial 5 as described above is mounted on a main body 50 of a film unit, on which a rear cover 55 and a front cover 56 are fixed. Reference numeral 58 designates a shutter blade. A reverse-rotation-preventing claw 51 is formed integrally with the main body 50 on its front side, and resiliently engages with a tooth of the wind-up dial 5, so that the wind-up dial 5 is kept from rotating reversely to the direction of winding up photographic film 57. The film unit 2 is contained in a housing body (not shown) of the underwater housing so as to bring the film wind-up dial 5 into mesh with a coupling gear 54 fixed on the housing dial 53. The coupling gear 54 is in mesh with the back of the wind-up dial 5 so as to push the wind-up dial 5 toward the front to a degree within its backlash. This might deform the claw 51 toward the front destructively. When this film unit 2 is allowed to stand in a hot place e.g. in direct sunshine, such deformation will remain permanently in the claw 51 whereby the degree of mesh with the wind-up dial 5 will decrease. The photographic film 57 may therefore fail to be wound up properly.
Although the wind-up dial 5 is made of an inexpensive material having a comparatively low density e.g. polystyrene, yet the coupling gear 54 is made of an engineering plastic material of a high density. When the housing dial 53 is rotated with an excessively high torque applied inadvertently and in the wrong direction, the teeth of the wind-up dial 5 will be damaged or broken, whereupon the photographic film cannot be wound.